1. Field of the Invention
The present invention relates to permanent magnet separators employed for removing ferrous materials from a product stream. More specifically, the present invention is directed toward permanent magnet separators having improved actuating features for cleaning the magnets.
2. Description of the Related Art
Permanent magnet separators are employed in many food processing operations and are even mandatorily required in some. They are also used in the manufacture of pharmaceuticals, in the chemical industry where process lines are alternatingly used for two or more incompatible products and wherever the highest degree of product purity is required. These devices often include a housing defining a hopper through which a number of non-magnetic tubes are mounted transverse to the product flow through the hopper. A plurality of magnets are located within the non-magnetic tubes. As the product flows past the tubes, ferrous particles are collected on the outer diameters thereof.
At various times during the product processing operations, the ferrous materials that collect on the tubes must be removed. To this end, the tubes are removed from the product flow area to a position typically outside the housing. A fixed plate or other wiper mechanism is disposed about the outer diameter of each tube to scrape the ferrous materials off the tube as it is withdrawn. The ferrous materials fall by gravity outside of the product flow area and onto the floor or into a collection receptacle. The tubes, and therefore the magnets housed therein, are then returned to their operative position transverse to the product flow within the hopper.
In the past, it has been known to actuate the tubes between their position transverse to the product flow within the hopper to the position outside of the hopper during the tube cleaning operation. This actuation was typically accomplished either manually or using pneumatic piston cylinder arrangements. Typically, a handle on the framework supporting the magnet was used by the operator to manually displace the magnet out of the hopper. On the other hand, the piston cylinder arrangements are operative to periodically reciprocate the tube assembly between their product flow and tube cleaning dispositions. The permanent magnet separators may be made "self-cleaning" by initiating movement of the tubes via the piston cylinder arrangement using controls.
Self-cleaning permanent magnet separators enjoy the advantage that they eliminate the need to shut down product lines to remove, clean and reinstall magnetic elements. Thus, self-cleaning permanent magnets make the cleaning of the tubes easier and more frequent cleaning prevents excessive iron contamination buildup on the magnets and assures maximum separating efficiency.
Despite these advantages, problems remain in the related art. For example, it is not uncommon for the pneumatic piston/cylinder arrangement to be subject to air of poor quality or low pressure. In these cases, it was not uncommon for the separator unit to fail or to not operate as designed with respect to cycle time or stroke distance of the magnet actuator. Additionally, where the climate is severe such as found outdoors or in northern regions, it was possible for the actuator unit to freeze. Further, where the permanent magnet separators are employed to filter very fine mesh products, the actuator unit can jam or not completely open or close from time to time and thus require more maintenance in the form of disassembly and cleaning. Recent analysis has also determined that the use of pneumatic piston/cylinder arrangements for magnet actuators add an unacceptable level of cost to the units. Furthermore, in larger applications, some permanent magnet separators become difficult, and sometimes impossible, to operate due to the force required to strip the magnets clean and the weight of the tubes as they are suspended during the cleaning operations.
Thus, there remains a need in the art for a permanent magnet separator which can quickly, efficiently and reliably clean the tubes in a cost-effective manner and which can be actuated either manually or automatically.